Field of the Invention
The present invention is in the field of making disk-shaped or wafer-shaped silicon bodies which can be used for solar cells on a continuous basis.
In the so called horizontal tape-drawing process for producing a silicon tape, a woven fabric preferably composed of graphite threads is employed as a carrier member and as a nucleator for crystallization. This fabric is drawn across a molten silicon bath in a tangential direction with heating sources are controlled such that considering the radiant losses of the melt surface, the silicon tape solidifies in a uniform thickness before it is drawn laterally from the melt. Such a procedure is disclosed, for example, by European Patent Application No. 0170119, corresponding to U.S. Ser. No. 755,587, now U.S. Pat. No. 4,664,745, whose disclosure is hereby incorporated by reference. Silicon tapes are thereby continuously manufactured with high drawing rates on the order of meters per minute. The silicon tapes are then divided into appropriate sections before further processing into solar cells.
In order not to disturb the continuity of the drawing process, the severing into sections of defined length must occur during the drawing process and with a constant drawing rate. The severing process must not place the tape under shock or under vibration because the growth process would thereby be disturbed. Growth disturbances lead to a reduction in the efficiency of the solar cells manufactured from this material.